1. Field of the Invention
This invention relates to processes for determining the electrical properties of materials.
2. Prior Art
It is known to determine the electrical properties of a material by inserting a probe into the material and transmitting electrical pulses to the probe to generate a reflected wave which is attenuated by the material. The reflected wave can be displayed and observed, with the configuration of the reflected wave indicating the electrical properties of the material being tested.
Two types of probes are commonly used for determining the electrical properties of materials. In one type, the probe is made up of a pair of parallel conductors spaced a predetermined distance apart. The disadvantage of this kind of probe is that the two conductors must always be maintained in a parallel relationship and the distance between the probes must remain constant from use to use.
The other type of probe is made up of a tubular outer conductor and inner conductor coaxial with the outer conductor, with an air space between the two conductors. The material to be tested is inserted into the tubular conductor to surround the inner conductor. The disadvantages of this system are that is not always easy to insert the material into the tubular conductor and it is almost always difficult to be sure that there is a minimum of air in the material after it is inserted into the tubular conductor.